Initial characterization of an unidentified A rmillaria isolate from S erbia using LSU ‐ IGS 1 and TEF ‐1‐α genes

Summary Armillaria species have a global distribution and play variable ecological roles, including causing root disease of diverse forest, ornamental and horticultural trees. Accurate identification of A rmillaria species is critical to understand their distribution and ecological roles. This work focused on characterizing an unidentified A rmillaria isolate from a S erbian forest using pairing, sequencing of the partial large subunit and intergenic spacer‐1 regions of r DNA ( LSU ‐ IGS 1) and the translation elongation factor‐1 alpha gene ( tef‐1α ) genes, and phylogenetic analyses. Despite previously obtained LSU ‐ IGS 1 RFLP patterns that matched the newly described N orth A merican A rmillaria altimontana , pairing tests and phylogenetic analyses of LSU ‐ IGS 1 and tef‐1α sequences clearly demonstrate that the unidentified isolate is not A . altimontana . Based on LSU‐IGS1, A rmillaria gallica isolates were polyphyletic, and the Serbian isolate clustered with a subset of European A .  gallica isolates within a well‐supported clade (99%). Based on tef‐1α , the Serbian isolate appeared as a separate, well‐supported clade (97%) that was basal to other poorly resolved, polyphyletic clades containing E uropean A .  gallica isolates. It is speculated that the unidentified A rmillaria isolate f rom Serbia could represent an evolutionary ancestral state because of its separate, basal position compared with other clades comprising polyphyletic E uropean A .  gallica isolates. Alternatively, this unidentified Serbian isolate could represent an unusual hybrid because of its high‐level sequence heterogeneity, represented by multiple two‐nucleotide codes, within tef‐1α . Further characterization is needed to confirm the taxonomic status and ecological/evolutionary significance of this unique, unknown A rmillaria isolate from S erbia.